Short-wave radio receiver with band-spreading



Aug. 12, 1941. T. A, sPooR 4 v 0 SHORI WAVE RADIO RECEIVER WITH BAND-SPREADING Fil ed May 9, 1940 70 BAA/D 51 7/7677 INVENTOR 7' l-IEODORUS A POOR ATTORNEY Patented Aug. 12, 1941 SHORT-WAVE RADIO RECEIVER WITH BAND-SPREADING Theodorus Antonius Spoor, Eindhoven, Netherlands, assignor to ltadio Corporation of America, New York, N. Y.

Application May 9, 1940, Serial No. 334,113 In Germany June 28, 1939 4 main-ls.

In the copending application of A. T. Vossen, Serial No. 297,972, filed October 5, 1939 there is described a device for obtaining band-spreading in short-wave reception.

The present invention relates to a radio receiver according to the above mentioned application having more than one short-wave range.

In such a receiver the case may occur that the bands to be spread are divided over more than one short-Wave range.

In band-spread reception the tuning means for band-spreading operate in this case on more than one short-wave range.

According to the earlier application the tun ing means for band-spreading are constituted, for example, by small variable inductance coils connected in series with the fixed inductance coils of the oscillatory circuits to be tuned. By means of these coils the total inductance of the oscillatory circuits can be varied by a certain percent.

When changing over to another short-wave range the inductance of the fixed inductance coil is varied. This entails the disadvantage that if the ratio of the inductances of the fixed and the variable inductance coils on the shortwave rang with the largest wavelength is correct, this relation, when changing over to another wavelength range, is too great to obtain a proper band-spreading on the bands situated in this short-wave range. In this case the transmitters are situated closely to one another on the tuning scale which remains for the greater part unused.

According to th invention this drawback is obviated by switching-over the tuning means for band-spreading when changing over from one short-wave range to another. Preferably, the switch by which the tuning means for bandspreading are changed over is mechanically coupled to the switch for wave-length changing.

The invention will be more clearly understood by reference to the accompanying drawing showing, by way of example, one embodiment thereof.

The drawing shows an oscillatory circuit l which can be tuned in two short-wave ranges and is also adapted for band-spread reception in each of these short-wave ranges.

In the position shown the oscillatory circuit is constituted by a variable tuning condenser 2, a fixed inductance coil 3 and a variable inductance coil 4 serving for band-spreading. Between the coils 3 and 4 are connected two series-connected switches 5 and 6 which are mechanically coupled. The mechanical coupling is diagrammatically shown by the link I.

When the two switches 5 and 6 are changed over, the coil 3 is switched out of circuit and a smaller coil 8 is connected in series with part of the variable inductance coil 4. For this purpose the coil 4 is provided with a tapping 9 whichmay be brought into connection with a contact of the switch 6.

The tapping 9 is so chosen that the percentage variation of the total inductance of the oscillatory circuit 1 obtained with the coil 4 is approximately the sam in either position of the switch.

The switches 5 and 6 may constitute part of the switch for Wave-length changing which already exists in the receiver for switching over to the intermediate and long-wave range.

What I claim is:

1. A tunable circuit for a multi-band receiver comprising a variable condenser, series-connect-ed fixed and variable inductances shunted across the variable condenser, a second fixed inductance, and means for replacing the first fixed inductance by the second and simultaneously including in circuit only a portion of the variable inductance.

2. A tunable circuit in accordance with the invention defined in claim 1 wherein the fixed and variable inductances are chosen of such values that the percentage of detuning by the variable inductance of the tunable circuit utiliz ing the first fixed inductance is at least approximately the same as the percentage of detuning by the included portion of the Variable inductance of the tunable circuit utilizing the second fixed inductance.

3. A multi-band radio receiver of the type utilizing in conjunction with a variable condenser one of a plurality of fixed inductance coils of difierent values which determine the band of frequencies to be received, means for selecting one of the fixed inductance coils to cooperate with the variable condenser, a variable inductance coil included in circuit with one of the fixed inductance coils and the variable condenser for effecting band spreading, the selecting means being constructed and arranged to include only a portion of said variable inductance coil upon operation of the selecting means to include another fixed inductance coil.

4. In a radio receiver, a circuit comprising a fixed inductance, a variable inductance and a variable capacity adapted to be tuned through a comparatively wide range of frequencies, the variable capacity serving to tune said circuit roughly to a plurality of comparatively narrow frequency bands within said Wide range of frequencies, the variable inductance serving as a fine adjustment tuning means for frequencies within the narrow frequency bands, a second fixed inductance and means for substituting the latter for the first mentioned fixed inductance 5 circuit only a portion of the variable inductance.

THEODORUS ANTONIUS SPOOR. 

